1. Field of the Invention
The present invention relates to an injection apparatus.
2. Description of the Related Art
Conventionally, in an injection molding machine, a screw is disposed within a heating cylinder of an injection apparatus such that it can rotate and can advance and retreat. By operating a drive mechanism, the screw can be rotated, and can be advanced and retreated. In a metering process, the screw is rotated, whereby a resin which is supplied from a hopper into the heating cylinder is melted through application of heat and transferred forward, and the molten resin is stored in a space located ahead of a screw head attached to the front end of the screw. In an injection process, the screw is caused to advance, whereby the molten resin, which is stored in the space located ahead of the screw head, is injected from an injection nozzle into the cavity of a mold apparatus so as to fill the cavity.
FIG. 1 is a conceptual view of a conventional injection apparatus.
In FIG. 1, reference numeral 11 denotes a heating cylinder. A screw 12 is disposed within the heating cylinder 11 such that it can rotate and can advance and retreat (move leftward and rightward in FIG. 1).
An unillustrated injection nozzle is attached to the front end (left-hand end in FIG. 1) of the heating cylinder 11, and a nozzle hole is formed in the injection nozzle.
The rear end (right-hand end in FIG. 1) of the heating cylinder 11 is attached to a front injection support 61, and a rear injection support 62 is disposed a predetermined distance away from the front injection support 61. The front injection support 61 includes a box-like body 61a and a cover 61b. Rods 63 extend between the front injection support 61 and the rear injection support 62, for maintaining a predetermined distance therebetween. The front injection support 61, the rear injection support 62, and the rods 63 constitute an injection frame.
A circular connection member 64 is integrally attached to the rear end of the screw 12 via a coupler 59. A cylindrical support member 65 is attached to the connection member 64 by use of bolts bt1. The connection member 64 and the support member 65 constitute a rotary slide member 68, which unitarily rotates with the screw 12. A male spline 92 is formed on the outer circumferential surface of a rear end of the support member 65.
In order to transmit rotation to the rotary slide member 68, a cylindrical rotary member 78 is disposed while surrounding the rotary slide member 68, and a female spline 93 is formed on the inner circumferential surface of the rotary member 78. The female spline 93 has an axial length equivalent to the stroke of the screw 12. The rotary member 78 is supported by bearings b1 and b2 in such a manner as to be rotatable relative to the front injection support 61.
An electrically operated metering motor 70 is disposed. In a metering process, the metering motor 70 is operated to rotate the rotary slide member 68, whereas, in the injection process, the metering motor 70 generates reverse torque to stop the rotation of the rotary slide member 68. The metering motor 70 includes an unillustrated stator, an unillustrated rotor disposed radially inward of the stator, an output shaft 74, and an encoder 70a attached to the output shaft 74 and adapted to detect the rotational speed of the metering motor 70, and is controlled on the basis of a detection signal output from the encoder 70a. Each of the stator and the rotor includes a core, and a coil wound onto the core.
An output gear 75, a counter drive gear 76, a counter driven gear 77, and the rotary member 78 are disposed between the metering motor 70 and the rotary slide member 68. The output gear 75 is attached to the output shaft 74. The output gear 75 and the counter drive gear 76 are engaged with each other. The counter drive gear 76 and the counter driven gear 77 are engaged with each other. The counter driven gear 77 is attached to the rotary member 78 by use of bolts bt3.
The output gear 75, the counter drive gear 76, the counter driven gear 77, and the rotary member 78 transmit to the rotary slide member 68 rotation generated through operation of the metering motor 70. For such operation, the rotary slide member 68 is disposed in such a manner as to be nonrotatable and axially movable relative to the rotary member 78; and the outer circumferential surface of the connection member 64 and the inner circumferential surface of the rotary member 78 are in slidable contact with each other. That is, the female spline 93 formed on the inner circumferential surface of the rotary member 78 is spline-engaged with the above-described male spline 92 to be slidable relative thereto.
Accordingly, when the output shaft 74 is rotated through operation of the metering motor 70, rotation is transmitted to the rotary slide member 68 via the output gear 75, the counter drive gear 76, the counter driven gear 77, and the rotary member 78, whereby the rotary slide member 68 is rotated in the regular direction or in reverse as needed, and thus the screw 12 is rotated accordingly. When the metering motor 70 is stopped and is caused to restrain the output shaft 74 by force of restraint, the rotary slide member 68 is caused to stop rotating, so that the screw 12 is caused to stop rotating.
A ball screw 83, which includes a ball screw shaft 81 and a ball nut 82 and serves as a direction-of-motion changing section, is disposed rearward (rightward in FIG. 1) of the front injection support 61. The ball screw shaft 81 includes a small-diameter shaft portion 84, a large-diameter threaded portion 85, a connection portion to be connected to an injection motor 90, etc. which are sequentially formed from the front end of the ball screw shaft toward its rear end. An annular flange member 89 is externally fitted to the shoulder between the shaft portion 84 and the threaded portion 85.
The electrically operated injection motor 90 is fixed to the rear injection support 62 via a load cell 96. The injection motor 90 is operated in the injection process. Rotation generated by the injection motor 90 is transmitted to the threaded portion 85. The above-described ball screw 83 converts a rotary motion generated by the injection motor 90 to a rectilinear motion accompanied by rotation; i.e., to a rotary, rectilinear motion, and transmits the rotary, rectilinear motion to the rotary slide member 68.
Thus, the ball screw shaft 81 is supported, at its front end by bearings b7 and b8, in such a manner as to be rotatable and axially immovable relative to the rotary slide member 68, and is rotatably engaged with and supported by the ball nut 82 at its center. That is, the rotary slide member 68 is disposed in such a manner as to be rotatable relative to the ball screw 83 and axially movable relative to the rotary member 78.
An unillustrated male screw is formed on a front end part of the shaft portion 84, and a bearing nut 80 is disposed while being engaged with the male screw. The bearing nut 80, together with a protrusion 65a formed on the inner circumferential surface of the support member 65, positions the bearing b7.
The ball nut 82 is fixedly attached to the rear injection support 62 via the load cell 96. The load cell 96 detects an injection force and a dwell pressure.
Accordingly, when rotation generated through operation of the injection motor 90 in the regular or reverse direction is transmitted to the ball screw shaft 81 via the connection portion, the ball screw shaft 81 is caused to advance or retreat while rotating, since the threaded portion 85 and the ball nut 82 are engaged with each other.
In the injection process or a like process, in which the rotary slide member 68 is caused to advance or retreat without rotation, stoppage of the operation of the metering motor 70 causes stoppage of the rotation of the rotary slide member 68, and the subsequent operation of the injection motor 90 causes the rotary slide member 68 to axially move. As a result, a rectilinear motion is transmitted to the screw 12, which is integrally attached to the rotary slide member 68, whereby the screw 12 is caused to advance (move leftward in FIG. 1).
Next, the operation of the thus-configured injection apparatus will be described.
First, in the metering process, when the metering motor 70 is operated, the rotation of the output shaft 74 is transmitted to the screw 12 via a transmission mechanism, which is composed of the output gear 75, the counter drive gear 76, the counter driven gear 77, the rotary member 78, etc., and the rotary slide member 68, to thereby rotate the screw 12 in the regular direction.
This rotation of the screw 12 causes unillustrated resin, which drops from an unillustrated hopper disposed on the heating cylinder 11, to advance along an unillustrated groove formed on the outer circumferential surface of the screw 12, and causes the screw 12 to retreat (move rightward in FIG. 1), whereby the resin is stored in a space located ahead of an unillustrated screw head attached to the front end of the screw 12. At this time, the force of retreat induced on the screw 12 causes the rotary slide member 68 to move relative to the rotary member 78; specifically, to retreat. As the rotary slide member 68 retreats, the ball screw shaft 81 is caused to retreat while rotating.
Next, in the injection process, the injection motor 90 is operated. The resultant rotation of the output shaft 94 is transmitted to the ball screw shaft 81 via the connection portion. The ball screw 83 converts the rotary motion to a rotary, rectilinear motion. As a result, the ball screw shaft 81 is caused to advance while rotating.
Then, when the metering motor 70 causes the rotary slide member 68 to stop rotating, the screw 12 is caused to advance without rotation, since the screw 12 is integrally attached to the rotary slide member 68.
Since the conventional injection apparatus requires the transmission mechanism and the rotary member 78 in order to transmit rotation generated by the metering motor 70 to the rotary slide member 68, noise arises from engagement of gears and other members, and the size thereof increases. Further, a large number of components are employed, resulting in emergence of torque loss and an increase in the cost of the injection apparatus.
Moreover, at the time of assembly, maintenance, etc. of the injection apparatus, the ball screw 83 is built into the injection apparatus along with the support member 65 and the bearings b7 and b8, and such building-in work must be performed in consideration of meshing engagement between the male spline 92 formed on the outer circumferential surface of the support member 65 and the female spline 93 formed on the inner circumferential surface of the rotary member 78. Therefore, when meshing engagement cannot be established properly at the spline portion, the building-in work requires a longer time, which deteriorates easiness of assembly, maintenance, etc.
An object of the present invention is to solve the above-mentioned problems in the conventional injection apparatus and to provide an injection apparatus capable of preventing generation of noise, enabling reduction in size, reducing the number of components, preventing emergence of torque loss, and reducing cost.
To achieve the above object, the present invention provides an injection apparatus which comprises an injection frame; a cylinder member attached to the injection frame; an injection member disposed within the cylinder member such that the same can rotate and can advance and retreat; a rotary slide member attached to the injection member; and a stator attached to the injection frame, and a rotor disposed radially inward of the stator to be rotatable relative to the stator.
The rotor comprises a hollow, cylindrical member disposed radially outward of the rotary slide member and movably relative to the rotary slide member, and a magnet attached to the cylindrical member.
In this case, the rotor comprises the cylindrical member and the magnet, and can transmit generated rotation directly to the rotary slide member, thereby eliminating the need for a transmission mechanism, which is composed of an output gear, a counter drive gear, a counter driven gear, a rotary member, etc., and preventing generation of noise, which would otherwise result from engagement of gears and other members. Thus, the number of components can be reduced; emergence of torque loss can be prevented; and the cost of the injection apparatus can be reduced. Further, since a space for disposition of the first drive section can be reduced, the injection apparatus can be reduced in size accordingly.
Since the rotor is equipped with a permanent magnet, a coil is not required to be disposed on the rotor, whereby the diameter of the cylindrical member can be increased accordingly. Thus, since the diameter of a direction-of-motion changing section can be increased, a direction-of-motion changing section having a large rated capacity can be incorporated, and heavy load molding can be performed. As a result, the injection apparatus can be reduced in size, and can be operated under heavy load molding conditions.
The injection apparatus may include casing formed integrally with the injection frame.
The stator and the rotor may constitute a first drive section for rotating the rotary slide member in a metering process.
The stator and the rotor may constitute a second drive section for axially moving the rotary slide member in an injection process.
The injection apparatus may includes a direction-of-motion changing section for converting a rotary motion generated at the rotor to a rectilinear motion and for transmitting the rectilinear motion to the rotary slide member.
Preferably, the direction-of-motion changing section comprises a first conversion element and a second conversion element; and the first conversion element is supported rotatably relative to the rotary slide member.
The present invention further provides an injection apparatus which comprises an injection frame; a cylinder member attached to the injection frame; an injection member disposed within the cylinder member such that the same can rotate and can advance and retreat; a rotary slide member attached to the injection member; a stator attached to the injection frame, and a rotor supported radially inward of the stator to be rotatable relative to the stator; and a rotational-speed detecting section for detecting a rotational speed of the rotor.
The rotational-speed detecting section includes an element to be detected, the element being attached to a hollow, cylindrical member to be rotated upon rotation of the rotor, and a detecting element disposed in opposition to the element to be detected.
In this case, the element to be detected is attached to the hollow, cylindrical member to be rotated through rotation of the rotor, and the detecting element is disposed in opposition to the element to be detected. Thus, in spite of use of the hollow rotor, the rotational speed can be detected, whereby metering can be performed smoothly.
Preferably, recesses and projections are formed on a detection surface of the element to be detected.
Preferably, a magnetized detection surface is formed on the detecting element.
Preferably, the element to be detected is disposed to face the detecting element in a non-contacting state.
Preferably, the cylindrical member is disposed radially outward of the rotary slide member and movably relative to the rotary slide member.
Preferably, the rotor includes the cylindrical member, and a magnet attached to the cylindrical member.
In this case, a magnet can be used for the rotor, and therefore, a coil is not required to be disposed on the rotor, whereby the size of the injection apparatus can be reduced.
Preferably, the rotational-speed detecting section detects pole position of the rotor.
The present invention further provides an injection apparatus which comprises: a frame; a stator attached to the frame to be located radially inward of the frame; a rotor disposed radially inward of the stator; and a rotary slide member disposed radially inward of the rotor, the rotary slide member being reciprocated along an axial direction.
At a rotation transmission section formed on a side face of the rotor, axial movement of the rotary slide member is permitted, and rotation of the rotary slide member is restricted.
Preferably, a lubricant chamber is formed between the rotary slide member and a cylindrical member which constitutes the rotor.
Preferably, a seal member is disposed on an outer circumference of the rotary slide member in such a manner that the seal member is in contact with an inner circumferential surface of a cylindrical member which constitutes the rotor.
The present invention further provides an injection apparatus wherein an airtight first lubricant chamber is formed between a frame and a rotor; and the first lubricant chamber is connected to a second lubricant chamber formed inside the rotor in order to supply lubricant to the second lubricant chamber.
Preferably, the first lubricant chamber is formed through disposition of a seal member between the frame and a rotation transmission section.